Various forms of spreaders have been either constructed or proposed for uniformly distributing granular or powder materials such as fertilizers and seeds over the ground. For example, U.S. Pats. No. 2,678,145, No. 2,761,589, No. 2,817,460, No. 2,839,222, No. 3,002,656, No. 3,015,416 and No. 3,180,530 each discloses a spreader of the push-type which is commonly used for fertilizing and seeding a lawn. Other forms of spreaders are constructed for towing over a lawn or field behind a motor driven vehicle. These types of spreaders are disclosed, for example, in U.S. Pats. No. 2,634,029, No. 2,835,420, No. 2,916,189, and No. 3,425,599.
The spreaders usually include a wheel supported hopper constructed of sheet steel which is either formed or deep drawn to form a part cylindrical bottom portion for the hopper, for example, as shown in above U.S. Pats. No. 2,678,145, No. 2,817,460 and No. 2,835,420. A series of longitudinally spaced openings or apertures are formed within the curved bottom wall or portion of the hopper, and a corresponding set of openings or apertures are formed within a curved sheet metal slide member which is supported directly below the curved bottom portion of the hopper for either longitudinally sliding movement or circumferential movement. Various mechanisms have also been proposed for adjusting the slide member, but the mechanisms commonly do not provide for precise adjustment.
The sheet metal hopper and slide member are usually painted prior to assembly. However, it is difficult to obtain a paint coating which provides substantial resistance to either abrasion or chemical corrosion by granulated fertilizer. The problems of corrosion and abrasion are particularly more pronounced on the curved bottom portion of the hopper below the rotary agitator and on the adjustable slide member. As a result, it is sometimes desirable to remove the slide member after using the spreader so that the hopper and slide member can be flushed and cleaned before the spreader is placed in storage. It is also not uncommon for fine solid fertilizer particles or seeds to lodge between the sheet metal bottom member and the sheet metal slide member and to bind the slide member so that it is difficult to adjust the slide member precisely for accurately controlling the flow of material through the apertures.
An increase in corrosion resistance has been obtained by forming the hopper and the slide member from a thin stainless steel sheet material. However, it is difficult to provide the bottom portion of the hopper and the slide member with sufficient rigidity to prevent lodging of some of the fine hard granular materials between the bottom portion of the hopper and the slide member so that the slide member can be easily adjusted. In addition, the sheet metal bottom portion of the hopper is easily dented by a stone or tree stump, resulting in binding of the slide member.